1. Field of the Invention
The present invention relates to a differential gear for distributing a driving force input into a differential case to a pair of output gears while a differential action therebetween is allowed.
2. Description of Related Art
As a differential device (a differential gear) for distributing a driving force to right and left wheels of a vehicle while a differential action therebetween is allowed, there is such a differential device including a differential lock mechanism that restricts a differential action between a pair of output gears (for example, see Japanese Patent Application Publication No. 2010-84930 (JP 2010-84930 A), Japanese Patent Application Publication No. 2015-102185 (JP 2015-102185 A)).
A differential device described in JP 2010-84930 A includes: a differential case; a pair of pinion gears pivotally supported by a pinion shaft fixed to the differential case; a pair of side gears (output gears) that mesh with the pair of pinion gears with their gear axes being at right angles; an intermittent member placed in an axially movable manner while engaging, in a rotation direction, with a hole portion provided in the differential case; and an actuator for axially moving the intermittent member.
The intermittent member has meshing teeth configured to mesh with one side gear out of the pair of side gears. The actuator includes an electromagnet and a moving member that axially moves by a magnetic force of the electromagnet. The electromagnet is constituted by an electromagnetic coil and a core placed so as to surround the electromagnetic coil. The moving member is constituted by a plunger made of a magnetic material, and a ring made of a nonmagnetic material that prevents a magnetic flux of the electromagnet from leaking out to the differential case. The moving member is placed inside the electromagnet, and the electromagnet and the intermittent member are axially arranged side by side.
When a current is applied to the electromagnet, the plunger moves toward an intermittent-member side, so that a ring presses the intermittent member via a plate fixed to the intermittent member. The intermittent member receives a pressing force at this time so as to move axially and mesh with the pair of side gears. This restricts a relative rotation between the differential case and one side gear, and along with this, a differential rotation between the pair of side gears is also restricted.
Similarly to the differential device described in JP 2010-84930 A, a differential device described in JP 2015-102185 A includes an intermittent member, and an actuator including an electromagnet and a moving member, and the moving member is constituted by a plunger and a ring. One axial end surface of the electromagnetic coil is opposed to a differential case, and the axial end surface is not covered with a core. When a current is applied to the electromagnet, a magnetic flux is generated in a magnetic path including the differential case, so that the plunger axially moves together with the ring by this magnetic flux. The intermittent member is pressed by the ring so as to mesh with one side gear, thereby restricting a relative rotation between the differential case and the pair of side gears.